Component for drilling and operating hydrocarbon wells

ABSTRACT

The tubular component ( 30 ) comprises a main body ( 32 ) of rotation about a longitudinal axis (X) of the component ( 30 ) provided, at least at one of its ends ( 34 B), with a first connector ( 36 B) for attaching the component ( 30 ) to another tubular component ( 30 ). The component ( 30 ) is moreover intended to be at least temporarily gripped in a peripheral zone (Z, Z 1 , Z 2 ) by means for retaining the component ( 30 ) on the operating facility ( 10 ). The component ( 30 ) comprises inside the zone (Z, Z 1 , Z 2 ) a coating ( 58 ) for protecting the component ( 30 ) against mechanical damage likely to be caused by the retaining means. In particular, the coating ( 58 ) being produced from a material with a hardness greater than the hardness of the material forming the component but less than a value of 70 HRC.

The present invention relates to the technical field of the exploitation of oil and gas deposits. It applies more particularly, but not exclusively, to the exploitation of offshore deposits, for example from platforms known more generally as “offshore” platforms.

The invention applies in particular to the components used in landing strings, for positioning tubes for casing, tubing or also various tools such as for example wellheads.

A landing string is formed principally by a series of tubular components, hereafter called landing tubes, and is attached to the string to be positioned. This landing string is thus generally intended to remain outside of the well, the main functions of this string being in particular to route the casing string to its final position in the well or also to cement the casing in the well, etc.

Conventionally, a landing tube differs from other operational tubes or casings by specific dimensional characteristics. In fact, the landing tubes must have a large tensile capacity. To this end, a landing tube generally has a diameter greater than 127 mm (or 5 inches) and a thickness greater than 12.7 mm (or 0.5 inches). However, the landing tube can be formed by a standard drilling tube used for a landing application.

In general, in order to form a landing string, landing tubes are placed end to end. Thus, a landing tube generally comprises a body rotating about a longitudinal axis of the component and two connectors, also called “tool-joints”, connected respectively to the ends of the body for attaching the tube to another tube. The connectors comprise for example male and female threaded elements that allow the tubes to be attached to each other by make up.

For positioning tubes, in the case of offshore operations, a certain length of string is extended from the platform to the seabed, from which the well is sunk, this length depending on the depth of the sea beneath the platform, which can sometimes reach several hundred metres, or even several kilometres.

The casing string is suspended from the landing string being formed, itself held on the platform by the last tube connected, hereafter called “surface tube”, the latter being held temporarily on the platform for the time it takes to add one or more tubes to the string being formed, increasing as much as the length of the latter.

The surface tube is secured to the platform using retaining means, themselves integral with a rotary table of the platform, which grip the tube like a vice. The retaining means generally comprise a plurality of slips having gripping elements on the surface, such as for example jaws, capable of being secured to the tube in order to retain it.

As a result, because of its function, the surface tube is subjected to very high axial tensile forces associated in particular with the mass of the string in the course of formation. This mass increases as the landing string forming operation progresses. This mass is of course greatest at the end of the operation and corresponds to the mass of the string extended between the surface and the bottom of the well and, in the case of the landing string, to the mass of the string extended between the surface and the seabed added to the mass of the tube string to be positioned in the well. The mass can then reach several thousand tonnes.

The clamping of the surface tube increases as the mass of the string increases. Thus, under the effect of very high tensile forces, the gripping elements leave an impression around the surface tube, promoting the appearance of cracks and other mechanical damage which embrittle the tube and reduce its period of use.

It has already been proposed in the state of the art, in particular in the document U.S. Pat. No. RE37,167 E filed by Grant Prideco, to solve the problem of the resistance of drilling tubes to the force exerted by the slips. This document teaches remedying this problem by manufacturing the tubes from a martensitic steel in order to limit the penetration of the slips into the material.

It has also been proposed in the state of the art, in particular in the document U.S. Pat. No. 3,080,179 filed by C. F. Huntsinger, to insert a portion of protective tube with an increased thickness between the connector and the main body of the component, at the level of a zone for clamping the component. However, the creation of an additional weld at the junction between this additional portion of tube and the body of the component presents an increased risk of the component breaking.

The purpose of the invention is in particular to propose a solution for best protecting the tubes of the landing strings against the mechanical damage to which the means of retaining on the platform are subjected without the drawbacks of the prior art.

To this end, a subject of the invention is a tubular component of a landing string for oil or gas extraction from an operating facility comprising a main body of rotation about a longitudinal axis of the component provided, at least at one of its ends, with a first connector for attaching the component to another tubular component, the component moreover being intended to be at least temporarily gripped in a peripheral zone by means for retaining the component on the facility, characterized in that the component comprises, inside the clamping zone, a coating for protecting the component against mechanical damage likely to be caused by the retaining means, the coating being produced from a material with a hardness greater than the hardness of the material forming the component but less than a value of 70 HRC.

Thanks to the invention, the coating, arranged as an interface between the tubular component and the retaining means, makes it possible to reduce the depth of the grooves likely to be formed by the retaining means on the component and thus to preserve the integrity of the component. This thus makes it possible to mitigate any defect that has begun to appear, but also to reduce any risk of crack initiation in the component clamping area.

Thanks to the physical hardness properties of the coating, the latter is ductile enough to deform, substantially following the profile of the galling surface of the retaining means, while being hard enough to ensure an effective protection of the tubular component. The relative ductility ensures a more homogeneous distribution of the stresses and thus a reduction in the stress concentration factor. The length of the coating is adapted for example as a function of the needs and dimensional constraints associated in particular with the retaining means and the practices of the user.

A component according to the invention can moreover comprise one or more of the following features:

-   -   the coating is a sacrificial coating;     -   the hardness of the coating increases progressively in the         direction from the component to the coating;     -   the coating is formed by a plurality of layers;     -   the peripheral clamping zone extends from an end face of the         first connector as far as at most one-third of the body;     -   the first connector has a female thread;     -   the component is provided, at the other of its ends, with a         second connector with a male thread;     -   the connector or connectors are connected to the body by         welding, forming a support joining the connector to the body;     -   the coating leaves the joint support exposed;     -   the thickness of the body is greater than 12.7 mm;     -   the coating has a roughness greater than the roughness on the         surface of the tubular component in order to facilitate the         adherence of the retaining means to the body of the component;     -   the thickness of the coating is greater than 1 mm and preferably         greater than 2 mm;     -   the coating is formed by a layer obtained by thermal spraying         for example of the electric arc type or by electroplating;     -   the main element or elements are selected from nickel, chromium,         molybdenum, tungsten and boron;     -   the secondary element or elements are selected from silicon,         carbon, chromium, boron, vanadium, titanium, iron, manganese and         aluminium;     -   the zone starts at the end of the body and extends for example         over approximately 1.5 metres.

Other characteristics and advantages of the invention will become apparent in the light of the following description, made with reference to the attached drawings, in which:

FIG. 1 represents an oil platform illustrating an assembly stage of a string of tubular components according to the invention;

FIG. 2 represents a detailed view of the oil platform of FIG. 1;

FIG. 3 represents a perspective view of a set of three tubular components according to the invention, dismantled;

FIG. 4 represents a partial section view of a tubular component according to the invention gripped in retaining means on the platform of FIG. 1;

FIG. 5 represents a diagrammatic view of a slip forming a part of the retaining means;

FIG. 6 represents a cross-section along a longitudinal axis of a tubular component of the set of FIG. 3;

FIG. 7 is a diagrammatic top view of a cross-section along the line 7-7 in FIG. 4.

A drilling facility denoted by the general reference 10 and in which the present invention can be used advantageously is shown in FIG. 1. In the described example, the facility 10 comprises an offshore platform 12, located on the surface of the sea or ocean.

This platform 12 is conventionally equipped with a certain number of accessories used for the drilling of the well and subsequent operation of the well. In the described example and as illustrated in detail in FIG. 2, the platform 12 comprises in particular a derrick 14 equipped with a rotary table 16 as well as numerous accessories that allow the handling and gripping of the various elements used to manufacture the well and exploit it. In a manner known per se, the rotary table 16 is capable of being actuated by means, not shown, which make it possible in particular to set in rotation, for example, a drill string of a well.

As illustrated in FIG. 1, the platform 12 comprises a floating support 18 in order to keep it substantially at the level of the surface S of the water. The platform 12 is thus located in line with an offshore well 20 drilled into the seabed F. The offshore well 20 may or may not have a casing. Moreover, as a variant, the platform 12 can optionally rest directly on the bed when the sea is less deep.

For the operation, the drilling, or also the manufacture of the well, the facility 10 also comprises a set of tubular components connected to one another in order to form strings with varying functions. Thus, for example, the strings can be intended for drilling the well. In this case, the term “drill string” is more accurately used. They can also be intended to produce a casing of the drilled well, or also to actually exploit the well or also to route such strings inside the well (landing strings). All of these strings are generally produced by placing tubular components end to end from the drilling platform 12.

As illustrated in FIG. 2, the facility 10 can also comprise a riser 22 which forms a pipe between the floating or semi-floating platform 12 and the well 20, and inside which one or other of the above-listed strings is extended. Its main function is in particular to protect the strings extending inside the pipe against the external environment. The riser 22 can for example be suspended from the platform 12.

In the example illustrated in the figures, the string being formed shown in FIG. 1 is a landing string 24. The production or casing tubes are generally positioned in two stages: a first stage of forming the string to be positioned and a second stage of forming the landing string which is carried out following the string to be positioned. Thus, in the example illustrated, this landing string 24 in the course of production is attached by its lower end 24A to another string 26 of tubular components, such as for example a casing string, and is attached by its upper end 24B to the platform 12. For example, the two strings 24 and 26 are attached to one another by means of a specific connection piece 28.

Thus, a portion of the landing string 24, in dismantled state, comprising three tubular components 30 is shown in FIG. 3. Preferably, each tubular component 30 comprises a main body 32 rotating about a longitudinal axis X and is provided, at least at one of its ends 34B, with a first connector 36B for attaching the tubular component 30 to another tubular component. For example, this first connector 36B has a female thread.

In this example, the tubular component 30 is also provided, at the other of its ends, with a second connector 36A with a male thread. As illustrated in FIG. 3, the tubular components 30 are capable of cooperating with one another by make up. The connectors 36 are connected to the body 32 by welding, forming a support 38 joining the connector 36 to the main body 32.

Generally, the tubular components 30 used to form the landing string 24 have a diameter greater than the diameter of the standard tubular components. For example, a diameter usual for this type of tube is greater than 127 mm (5 inches). Moreover, such a component generally has an increased thickness, for example greater than 12.7 mm (0.5 inches). Moreover, the tubular components are preferably produced from a material of a grade higher than 105 KSI (725 MPa) and more commonly higher than 135 KSI (931 MPa). Such properties allow them to withstand the very high tensile forces associated with the mass of the string that they are supporting. However, as a variant, the landing tube can be formed by a drilling tube.

As illustrated in FIG. 2, in order to produce such assemblies and to hold them on the platform 12, the facility 10 is equipped with means 40 for retaining tubular components 30. As can be seen in this figure, the retaining means 40 comprise for example a lower head 42 for securing the tubular component 30, and therefore the string in the course of production, to the platform 12. This lower head 42 makes it possible to retain the string on the platform 12, by gripping the last tubular component connected 30, i.e. by the upper end 24B of the string being formed 24. As can also be seen in FIG. 2, the retaining means 40 also comprise an upper head 44 for suspending and raising a tubular component 30 (or several components) in order to connect it to the last component of the portion of string 24 already formed. It can thus be seen in FIG. 2 that a first tubular component 30 is suspended by the upper head 44 while a second tubular component 30, at the upper end of the string 24, is secured to the platform 12 by the lower head 42.

The lower 42 and upper 44 heads of the retaining means 40 are shown in detail in FIG. 4. Preferably, the lower head 42 comprises at least one slip 46. In the described example, the lower head 42 comprises a plurality of slips 46, for example three (FIG. 7), capable of substantially following the shape of the body 32 of the tubular component 30 and gripping it in a vice-like manner. The lower head 42 moreover preferably comprises a main body 48 formed in this example by the rotary table 16. The rotary table 16 thus comprises a housing 50 for receiving the slips 46. In the described example, the lower head 42 also comprises adaptation parts 52 positioned between the slips 46 and the rotary table 16 making it possible to facilitate the positioning of the slips 46 inside the body.

A detailed view of a slip 46 is shown in FIG. 5. The slip 46 thus in this example has the general shape of a cone portion and has a gripping surface 54 for retaining the component. For example, the lower head 42 comprises a plurality of gripping elements 56, for example of the jaw type, capable of grasping the tubular component 30. Each gripping element 56 is formed for example by a strip produced from treated steel. Moreover, the upper suspension head 44 comprises, as illustrated in detail in FIG. 4, a main body provided with an orifice for guiding the tubular component and is connected to a lifting device 47 shown diagrammatically in FIG. 2.

As can be seen in FIGS. 4 and 6, the tubular component is intended to be at least temporarily gripped inside a peripheral zone Z for clamping the component by the retaining means 40. In this example, this zone Z extends from one end edge of the first connector 36B as far as at most one-third of the body 32. In this example, the zone Z comprises first Z1 and second Z2 zones:

-   -   a first zone Z1 for gripping the component 30 by the lower head         42,     -   a second zone Z2 for gripping the component 30 by the upper head         44.

Generally, a tubular component 30 has a length comprised between eight and fourteen metres (i.e. approximately 25 to 45 feet). In the example illustrated, the tubular component 30 has a standard length of ten metres (approximately thirty feet). In this case, the zone Z extends for example as far as two metres (eighty inches), i.e. less than one-third of the standard length of the component 30. Preferably, the zone Z starts at 0.5 metres (nineteen inches) from the end edge of the female connector 36B, which corresponds approximately to the standard length of the female connector 36B of such a tube. The zone Z extends in this case over a length of 1.5 metres (sixty inches) along the axis X of the tubular component 30. Moreover, the first zone Z1 extends for example over 0.5 metres (approximately 20 inches) and the same applies to the second zone Z2. These two zones Z1 and Z2 are distinct in the described example. However, optionally, in a variant not illustrated, the two zones Z1 and Z2 can overlap at least partially. The delimitation of this zone Z or of these two zones Z1 and Z2 depends on different parameters, such as the dimension of the tubular components, the retaining surface of the retaining head, the connector length 36B, etc.

According to the invention, in order to protect the component 30 against mechanical damage likely to be caused by the retaining means 40, and in particular by the jaws of the lower head 42, the component 30 comprises a protective coating 58. More particularly, the coating 58 is produced from a material with a hardness greater than the hardness of the material forming the component 30 but less than a value of seventy Rockwell, on the C scale (unit known by the acronym HRC), preferably less than a value of fifty HRC.

In this example, the jaws are produced from a material with a hardness substantially equal to 55 HRC and preferably, the coating 58 is produced from a material with a hardness less than the hardness of the material of the jaws, therefore less than 55 HRC. During the clamping of the component by the jaws the relative ductility of the coating 58 compared with the jaws causes a deformation of the coating 58 according to the surface profile of the jaws and thus a homogeneous distribution of the stresses. Moreover, the relative hardness of the coating 58 compared with the tubular component 30 ensures an effective protection of the component 30. Thus, for example, the tubular component 30 has a hardness value substantially equal to twenty-eight HRC.

The coating 58 is for example produced from a metal alloy in which:

-   -   the main element or elements are selected from nickel, chromium,         molybdenum, tungsten and boron,     -   the secondary element or elements are selected from silicon,         carbon, chromium, boron, vanadium, titanium, iron, manganese and         aluminium.         The quantities of the different elements of the alloy are chosen         so as to obtain the hardness characteristics required by the         invention.

For example, an alloy composition suitable for the invention comprises 45% chromium, 6% boron as main elements and silicon (2%), carbon, iron and sulphur (less than 0.1%) as secondary elements. A hardness of 58 HRC is measured.

Another suitable composition comprises 20% chromium, 15% molybdenum, 10% tungsten as main elements and carbon (<2%), manganese (<5%), silicon (<2%), boron (<5%) and iron as secondary elements. A hardness of 54 HRC is measured.

Preferably, the coating 58 is produced by thermal spraying. This is a method consisting of spraying heated particles of the material to be applied to a surface of the tubular component, for example prepared beforehand by sanding or shot-blasting. The accumulation of the particles on the component 30 forms the coating 58. This method has in particular the advantage of preventing the tubular component 30 from being exposed to temperatures that are too high and may damage its mechanical integrity. In fact, the particles are heated and cooled again when sprayed onto the surface of the tubular component 30.

For example, the coating 58 can be produced by means of an electric arc thermal spraying method. This method is based on melting one or more wires formed by the material to be sprayed, by means of an electric arc. Preferably, the molten material is atomized by a compressed gas, for example air, and is thus sprayed onto the part to be hard-surfaced. This method makes it possible to obtain a coating with a high adherence and low porosity thanks in particular to the combination of a high spraying speed and a high temperature.

As a variant, the coating 58 can be produced by electroplating. In this case, the product used is generally a composition based on nickel sulphamate. The coating 58 obtained then in this example has a Rockwell hardness of fifty HRC.

Preferably, the hardness of the coating 58 increases progressively in the direction from the component 30 to the coating 58. This property of the coating 58 makes it possible in particular to ensure better adhesion of the coating to the body of the tube. In order to produce this hardness progression, it is desirable to form a coating 58 comprising a plurality of layers, each of the layers being produced from a material with a predefined hardness and a value that increases in the direction from the component 30 to the coating 58.

Moreover, in the described example, the coating 58 has a thickness greater than 1 mm and preferably greater than 2 mm. This minimum thickness makes it possible to ensure a sufficient protection of the component with regard to the depth of the imprints likely to be produced for example by the jaws of the lower head 42.

According to the invention, the coating 58 extends inside the peripheral clamping zone Z. In this example, the coating 58 very largely, or even completely, covers the first zone Z1 and preferably also the second zone Z2. It may be envisaged to cover all of the zone Z or only the first zone Z1 or also only the first Z1 and second Z2 zones. A person skilled in the art knows how to suitably adjust the dimensions of the coating 58 in order to reap the benefits provided by the invention as a function of the different constraints of the facility. The delimitation of the zones Z1 and Z2 and thus of the zone Z depends on the dimensional constraints of the retaining means and/or on the practices of the users.

Moreover, the coating 58 preferably leaves the joint support 38 exposed. For example, the coating 58 extends below the joint support 38 of the female connector 36B and the body 30 as illustrated in FIG. 6. The joint support 38 remaining uncovered thus forms a visual marker in order, during the positioning of the lower 42 and upper 44 heads for gripping the component, to prevent the latter from accidentally gripping the component 30 around the joint support 38 which forms a relatively fragile region of the component 30. In this figure, the body 32 has a general cylindrical shape. Of course, this representation is diagrammatic. In a variant, the body 32 can thus have a profile with variable thickness. For example, the body can locally have a thin section formed by a reduction in its external diameter and/or an increase in its internal diameter. In this case, the coating can extend at least partially around the thinned zone of the tube body.

Preferably, the coating 58 is a sacrificial coating. It can thus optionally be replaced in the event of its significant degradation.

In order to facilitate the adherence or securing of the lower head 42 to the component 30, the coating 58 preferably has a roughness greater than the surface roughness of the tubular component 30. For example, in order to achieve the desired roughness, various technical means can be implemented, such as machining, localized or wide-spread grinding, etc.

The main aspects of operation of a tubular component 30 according to the invention will now be described. Initially, the landing string 24, as illustrated in FIG. 2, is in the course of formation and is suspended from the platform by a tubular surface component. This component is gripped by the lower head 42. Once the tubular component or components suspended from the surface component have been connected, the string of components in the course of production is lowered a distance substantially equivalent to the length of the tubular components added. This handling operation is accomplished, on the one hand, for example, by means of the upper suspension head which is supported by an elevator link connected to the lifting system of the platform (not shown) and, on the other hand, by means of the lower gripping head which is capable of releasing the surface component in order to allow the string being formed to be lowered to the last newly connected component. The further the operation of forming the string progresses, the greater the tensile forces generated by the weight of the string on the gripped surface component.

Thanks to the invention, the last temporarily-gripped surface component is protected by the coating 58 against mechanical damage likely to be caused in particular by the gripping elements of the retaining head. Moreover, when this coating 58 is too damaged and its efficacy is consequently reduced, it can advantageously be replaced without damaging the component 30 itself. This makes it possible to prolong the life of such tubular components 30.

Of course, other embodiments can be envisaged without exceeding the scope of the invention. Thus, various modifications can be made by a person skilled in the art to the invention which has just been described by way of example. 

1. Tubular component (30) of a landing string for oil or gas exploitation from an operating facility (10), comprising a main body (32) of rotation about a longitudinal axis (X) of the component (30) provided, at least at one of its ends (34A, 34B), with a first connector (36B) for attaching the component (30) to another tubular component (30), the component (30) moreover being intended to be at least temporarily gripped in a peripheral zone (Z) by means (40) for retaining the component (30) on the facility (10), characterized in that the component (30) comprises, inside the clamping zone (Z), a coating (58) for protecting the component (30) against mechanical damage likely to be caused by the retaining means, the coating being produced from a material with a hardness greater than the hardness of the material forming the component (30) but less than a value of 70 HRC.
 2. Component (30) according to the previous claim, in which the coating (58) is a sacrificial coating.
 3. Component (30) according to one or other of the previous claims, in which the hardness of the coating (58) increases progressively in the direction from the component (30) to the coating (58).
 4. Component (30) according to any one of the previous claims, in which the coating (58) is formed by a plurality of layers.
 5. Component (30) according to any one of the previous claims, in which the clamping zone (Z) extends between an end face of the first connector (36B) as far as at most one-third of the body (32).
 6. Component (30) according to one or other of the previous claims, in which the first connector (36B) is of the type having a female thread.
 7. Component (30) according to the previous claim, being provided, at the other (34A) of its ends (34A, 34B), with a second connector (36A) with a male thread.
 8. Component (30) according to any one of the previous claims, in which, the connector or connectors (36A, 36B) being connected to the body (32) by welding, forming a support (38) for joining the connector (36A, 36B) to the body (32), the coating (58) leaves the joint support (38) exposed.
 9. Component (30) according to any one of the previous claims, in which the thickness of the body (32) is greater than 12.7 mm.
 10. Component (30) according to any one of the previous claims, in which the coating (58) has a roughness greater than the surface roughness of the tubular component (30) in order to facilitate the adherence of the retaining means (42) to the body (32) of the component (30).
 11. Component (30) according to any one of the previous claims, in which the thickness of the coating (58) is greater than 1 mm and preferably greater than 2 mm.
 12. Component (30) according to any one of the previous claims, in which the coating (58) is formed by a layer obtained by thermal spraying, for example of the electric arc type, or by electroplating.
 13. Component (30) according to any one of the previous claims, the coating (58) is formed by a metal alloy comprising at least one or more main elements chosen from nickel, chromium, molybdenum, tungsten, boron.
 14. Component (30) according to the previous claim, in which the metal alloy comprises at least one or more secondary elements chosen from silicon, carbon, chromium, boron, vanadium, titanium, iron and aluminium.
 15. Component (30) according to any one of the previous claims, in which the zone (Z) starts at the end of the body and extends for example over approximately 1.5 metres. 